For extended power failures, the best safeguard is a generator. CompTIA Security+ SY0-701 emphasizes that generators are designed to provide long-term, sustained power, unlike UPS systems, which only supply temporary emergency power.
Generators ensure that critical operations-including data centers, communication systems, and security infrastructure-stay online for hours or days, depending on fuel capacity. This matches the requirement for mitigating "extended" outages.
UPS units (C) protect against short-term outages and provide time for graceful shutdown or generator startup, but cannot support prolonged power consumption. Batteries (B) provide the least protection and run out quickly. Off-site backups (A) do not maintain operational continuity; they simply preserve data.
Disaster recovery and business continuity planning in SY0-701 highlights generators as essential components for maintaining availability, a core principle of the CIA triad. Generators prevent downtime, maintain productivity, and keep essential systems functioning throughout prolonged outages, making D the best answer.